ITTO930678A1 - ACCELERATION SENSITIVE DEVICE. - Google Patents

Description

DESCRIPTION of the industrial invention entitled -. "Acceleration sensitive device?".

1. Field of the Invention

The present invention relates to an acceleration sensitive device mounted on an automatic shut-off valve having an integrated microcomputer and used in city gas appliances. and commercial propane gas equipment or mounted on control devices of domestic oil heaters, gas combustion equipment and electrical equipment, to detect an oscillation, such as an earthquake, thus providing a detection signal to the automatic shut-off valve or control devices.

2. Description of the prior art

The prior art has proposed several types of seismosensitive devices. The Japanese publicly available patent application (Kokai) No.

63-29286 (1988), what will it be? referred to as "first reference", describes a seismosensitive device in which a seismosensitive valve operates a first contact in response to an earthquake of a predetermined or greater seismic intensity by causing it to engage with a second contact. intended to automatically maintain its horizontal condition in an enclosure. Japanese Publicly Available Patent Application (Kokai) No.

2-186224 (1990), what will it be? referred to as "second reference", describes a seismic sensitive device in which a seismic sensitive sphere rolls in a housing so that a movable contact suspended above the sphere engages with, and separates from, a fixed contact disposed in the inner shell. The housing? suspended in an outer casing with a liquid that fills it. Publicly Available Japanese Patent Application (Kokai) No. 64-79624 (1989), what will it be? referred to as the "third reference", describes a seismosensitive device in which a mercury globule is enclosed in a metal housing.

The seismic-sensitive devices have recently been mounted on automatic shut-off valves having an integrated microcomputer and used in city gas appliances. and commercial propane gas equipment. An oscillation due to an earthquake or similar? detected by the seismosensitive device, which generates cos? a detection signal. The signal ? supplied to the automatic shut-off valve in order to take the necessary countermeasures. In these valves, the oscillation due to the earthquake must be distinguished from an oscillation produced by the collision of a flying object with the valve and an artificial noise produced by the passage of a truck or similar, civil engineering works and the like. For this purpose, the seismic-sensitive device must have predetermined operating characteristics in one frequency band of the oscillation due to the earthquake and different operating characteristics in the other frequency band. The first reference mentioned above says nothing about this requirement. Pi? in particular, in the described seismosensitive device, the mobile contact? maintained between the fixed contact and the sphere which acts only as a source of motion of the moving contact when the moving contact? brought into engagement with the fixed contact. However, in reality? occurs the substantial collision of the sphere with the fixed contact, since? both members are rigid bodies, and a resulting repulsion causes the sphere and the moving contact to instantly move away from the fixed contact. This construction can not? ensuring a long contact time period as desired and consequently a duration of an "on" signal cannot be ensured. be made long when the seismic sensitive device acts as a switch. What? the oscillation due to the earthquake can not? be distinguished from that due to man-made noise or electrical noise when the device described in this reference? used to detect the oscillation due to the earthquake.

The mobile contact? suspended with a support point slightly more? high of the center of gravity of the seismic-sensitive device described in the second reference mentioned above, which increases the number of parts and complicates the construction of the seismic-sensitive device. Consequently, the seismic-sensitive device has difficulty? assembly and miniaturization. Moreover, this seismosensitive device can not? provide a long period of contact time as in the device of the first reference. The second reference describes that the repulsion due to the collision of the moving contact with the fixed contact? absorbed by elastic organs preventing co3? that the contact is instantaneous. However there? further increases the number of parts and complicates construction. Bench? this reference also describes that the seismosensitive sphere can? be made small since? the movable contact moves with the sphere, a friction between the sphere and the movable contact prevents the miniaturization of the sphere. In addition, the housing that encloses the sphere? made of an insulating material. When the insulation material? a synthetic resin,? organic contaminants are likely to be produced causing an interruption of the electrical conduction between the contacts. The cost of manufacturing the seismic-sensitive device? increased when the insulation material? a glass or ceramic. Furthermore, the rolling of the ball or its collision with the moving contact deforms in particular protruding or corner parts of the housing when the housing? made in synthetic resin. Consequently, the initial operational characteristics cannot be obtained after a certain period of service.

The seismosensitive device employing mercury as described in the third reference? a high performance switch having characteristics which correspond to control by means of a microcomputer and which provides stable performance over a long period of time. However, a seismosensitive device in which no mercury is used? been recently desired from the point of view of environmental protection.

In light of the foregoing discussion, a small, rigid, cost-effective, cost-effective seismosensitive device suitable for mass production is desired. Mercury should not be used in the seismosensitive device but nevertheless it should have the same operational characteristics as the si3mosensitive device employing mercury. In this respect, however, the construction of the seismosensitive device that employs the mercury globule cannot? be automatically applied to the seismosensitive device in which the solid conductive sphere is used, since? the mercury globule? liquid.

SUMMARY OF THE INVENTION

So? a primary object of the present invention is to provide an acceleration-sensitive device in which stable electrical contact between parts making up a pair of contacts can be ensured and a desired contact time period can be achieved in a stable manner.

Another object of the invention is to provide a device sensitive to acceleration in which the oscillation due to the earthquake can be clearly distinguished from that due to other noise.

Furthermore, another object of the invention consists in realizing an acceleration sensitive device which is rigid, of simple construction and of limited dimensions.

To achieve these objects, the invention provides an acceleration-sensitive device which includes a seismic-sensitive element. The seismic-sensitive element comprises an enclosure formed from an electrically conductive material and having a bottom and an end. open, in which the envelope has an inclined face formed on its bottom that rises gently concentrically outwards substantially from the center of its bottom. A warhead? fixed to the casing in order to close its end? open and has a through opening in which? attached an electrically conductive terminal plug in an isolating relationship with the cylinder head. A contact member made of an electrically conductive material? fixed at one end of the terminal plug located inside the enclosure. Does the contact organ have a multiplicity? of tab portions comprising respective contact portions disposed concentrically with the terminal pin, wherein the tab portions have an elasticity. predetermined. An inertial sphere? enclosed in the casing so as to be arranged substantially in the center of the casing in a normal attitude thereof in a stationary condition. Does the inertial sphere move when? subject to oscillation, so that the inertial sphere rolls on the tongue parts of the contact member except the ends? distal parts of the tab parts so that the inertial sphere realizes an electrical conduction between the contact member and the casing and so that the tab parts are elastically deformed, thus receiving? a force that causes it to push against the bottom of the shell.

According to the seismic-sensitive element previously described, the inertial sphere moves when? subject to oscillation. The inertial sphere slides on the tongue parts of the contact member, deforming them elastically, thus receiving? the force that pushes it against the bottom of the enclosure. This construction stabilizes the contact of the inertial sphere with the contact member and the bottom of the casing. Consequently, the oscillation due to the earthquake can? be distinguished from that due to the other noise since? the electrical contact operation can? be stabilized and? a desired contact duration can be ensured.

Preferably a rebound force based on a resultant force (F2 + F3) of a composite force (F2) of a frictional force (Fi) between the inertial sphere and the tab parts in a range of motion of the inertial sphere, which composite force (F2) acts in a direction parallel to the bottom of the shell, and a friction force (F3) between the inertial sphere and the bottom of the shell,? determined to be less than a resultant force (F4 + F5) of a composite force (F4) of a repulsion force applied to the inertial sphere by the tongue parts of the contact member, which composite force (F4) acts in a direction parallel to the bottom of the enclosure.

The invention also provides an acceleration sensitive device, suitable for a tilt switch, comprising a casing made of an electrically conductive material and having a bottom and an end. open, in which the casing has a central neutral recess in the bottom and a rolling face around the recess so that the bottom has the shape of a shelf, a head fixed to the casing so as to close the end? open and having a through opening in which an electrically conductive terminal plug is fixed in an insulating relationship with the head, a contact member formed of an electrically conductive material and fixed at one end? of the terminal plug arranged inside the casing, in which the contact member has a contact part arranged concentrically with the terminal plug, and an inertial sphere enclosed in the casing so as to be arranged in correspondence with the recess of the bottom of the envelope in its normal attitude in a steady state due to gravity so that the inertial sphere cannot be brought into contact with the contact organ. The rolling face of the bottom of the casing? made so that it rises concentrically outward from the center of its bottom and so that its gradient decreases. The inertial sphere cannot? roll on the rolling face of the bottom of the enclosure due to its neutral recess until the enclosure? inclined of a predetermined angle, thus preventing? that comes into contact with the contact organ. The inertial sphere can? move away from the neutral recess by rolling so? on the rolling face when the wrap? inclined more? of the predetermined angle, so that the inertial sphere is brought into contact with the contact member, thus connecting? electrically the contact member to the casing.

Other objects of the present invention will become obvious from the understanding of the illustrative embodiments which will be described with reference to the accompanying drawings. Several advantages not mentioned herein will be evident to those skilled in the art in practicing the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the present invention will be described with reference to the attached drawings, in which:

figure 1 represents a longitudinal section view of a seismic-sensitive element of a first embodiment according to the invention;

Figure 2 is a partially enlarged sectional view of the seismic-sensitive element;

figure 3 represents a graph showing operational characteristics of the seismic-sensitive element;

Figure 4 is a schematic diagram to explain the operation of the seismic-sensitive element;

Figure 5 is a longitudinal sectional front view of a seismic-sensitive device in which? incorporated the seismosensitive element;

figure 6 is a longitudinal sectional side view of the seismic-sensitive device;

figure 7 represents a longitudinal section view of the seismic-sensitive element of a second embodiment;

figure 8 represents a longitudinal sectional view of the seismic-sensitive element of a third embodiment;

figure 9 represents a longitudinal sectional view of the seismic-sensitive element of a fourth embodiment;

Figure 10 is a longitudinal section view of the seismic-sensitive element of a fifth embodiment;

Figure 11 is a partially enlarged view of a contact plate used in the seismic-sensitive element of the fifth embodiment;

figure 12 represents a partial perspective view of the seismic-sensitive element of a sixth embodiment;

figure 13 represents a longitudinal sectional view of the seismic-sensitive element of a seventh embodiment;

Figure 14 is a longitudinal sectional view of a modified form of the seismic-sensitive element of the first embodiment illustrated in Figure 1;

Figures 15, 16 and 17 show modified shape views of the contact plate used in the seismic-sensitive element, respectively;

Figure 18 is a longitudinal sectional view of a tilt switch in accordance with an eighth embodiment;

Figure 19 is a partially enlarged view of a neutral recess of the tilt switch on which an inertial sphere rests;

Figure 20 is a longitudinal sectional view of the tilt switch of a ninth embodiment;

Figure 21 is a partially enlarged view of the neutral recess of the tilt switch on which the inertial sphere rests, in the ninth embodiment;

Figure 22 is a longitudinal sectional view of the tilt switch of a tenth embodiment in its inverted position;

23 is a partially enlarged view of the tilt switch, showing a head having a terminal pin at one of the ends of which ? contact plate fixed;

Figures 24, 25 and 26 show modified shape views of a tilt switch housing, respectively; And

Figure 27 is a longitudinal sectional view of the tilt switch of an eleventh embodiment.

DESCRIPTION OF THE PREFERRED FORMS OF IMPLEMENTATION

The first embodiment of the invention will be now described with reference to Figures 1 to 6. Figure 1 illustrates a seismosensitive element 1 used in a seismosensitive device according to the present invention. The seismic-sensitive element 1 comprises a casing 2 and a head 3 each made of an electrically conductive material, such as a metal. The casing 2? made in a cylindrical shape and has an end? open and a bottom. The head 3 has an opening 4A formed therethrough. An electrically conductive terminal plug 6? fixed in the opening 4A by means of an electrically insulating filling material 5, such as glass or ceramic, so as to extend through this opening. A contact plate 7 which acts as a fixed contact? fixed at one end? of the terminal plug 6 arranged in the casing 2, for welding or the like. The contact plate 7 Jia a multiplicity? of tab portions 7A extending radially from its center and each having an elasticity enough. An electrically conductive massive inertial sphere 8 acting as a moving contact? enclosed in the casing 2. The inertial sphere 8 can? be made of cast iron, stainless steel, copper, its alloys and hard lead. In this respect, cast iron, copper and the like are easily oxidized in atmospheric air and consequently there? the possibility? that a resulting oxide film could compromise conductivity? of the inertial sphere 8. It is preferable that the surface of the inertial sphere is treated with a noble metal such as gold or silver or by plating of nickel or an alloy of lead and tin. The head 3 is fixed to the casing 2 by means of an annular projection so as to close its end. open.

Is the air in housing 2 airtight? unloaded and instead the casing 2? filled with a volume of gas intended to prevent contamination, such as hydrogen, helium, argon or nitrogen, so that the contact plate 7, the inertial sphere 8 and the inner face of the casing 2 can be protected from corrosion and contamination, allowing to obtain stable operating characteristics for a long period of service.

The bottom 2B of the casing 2 comprises an inclined face. The tilted face? a conical face obtained by rotation of a straight line with an inclination 2C in the embodiment. The shape of the slanted face is not? limited to this. For example, you can? treat of a conical face whose inclination varies progressively. Also you can? treat of a concave or convex face obtained by rotation of a curve with a vertically uniform curvature. The inclination previously described? defined as an angle of a straight line between a point of contact of the inertial sphere on the inclined face in its stationary position and a point of contact of the inertial sphere on the inclined face in a position assumed by the inertial sphere when yes? rolled away from the stationary position. The curvature of any previously mentioned curve can? be varied in steps or gradually unless its direction of inclination changes.

The lower face 2B of the casing 2? provided with a central recess 2A which acts as a support part to keep the inertial sphere 8 in position until? subject to an oscillation of a predetermined amplitude. Without the support part, the inertial sphere would tend to roll in response to even a slight oscillation, which would make the operating characteristics of the element close to its response threshold unstable and would cause vibrations between the contacts. The dimension of the recess 2A depends on the diameter of the inertial sphere 8 and on a predetermined oscillation acceleration to which the element responds. The oscillation acceleration a (threshold value) that causes the inertial sphere 8 to start rolling? obtained from the following equation (1):

r? g

a = - (1)

-JEF - r *

wherein R represents a radius of the inertial sphere 8 and _r represents a radius of the recess 2A.

For example, now consider the case in which the seismic element? intended to be sensitive to the earthquake of intensity? seismic 5. In this case, the oscillation acceleration that causes the inertial sphere 8 to start rolling? obtained approximately as 100 gal from the previous equation (1) when the radius R of the inertial sphere 8? 3 mm and the radius r of the recess 2A which acts as a support part? 0.3 mm. The acceleration of oscillation? approximately 250 gal when the radius of the inertial sphere R? 3 mm and the radius of the recess r? 0.75 mm. A field defined by these acceleration values d? oscillation corresponds approximately to an acceleration range of oscillation between 80 and 250 gal for an intensity? seismic 5. Consequently, the oscillation acceleration that causes the inertial sphere 8 to start rolling can? be fixed in the field corresponding to an intensity? seismic 5 when the radius of the supporting part assumes a value between 0.1 and 0.25 times smaller than the radius of the inertial sphere 8.

Sar? now described the operation of the seismosensitive element 1. The inertial sphere 8 rests on the recess 2A when? stationary in its normal attitude. In this condition, the inertial sphere 8? positioned at a distance from the contact plate 7 and consequently the terminal plug 6 not? electrically connected to the casing 2 or to the metal head 3. When? subject to an oscillation, the inertial sphere 8? kept resting on the recess 2A until the predetermined oscillation acceleration is reached, which depends on the radii of the inertial sphere and of the recess. When the predetermined oscillation acceleration is reached, the inertial sphere 8? made to move out of the recess 2A, rolling 3 on the lower face 2B of the casing 2. Rolling on the lower face 2B, the inertial ball 8 comes into contact with the tab parts 7A of the contact plate 7. Consequently, an electrical path is closed with the terminal plug 6, the contact plate 7, the inertial sphere 8, the casing 2 and the cylinder head 3. A resulting electrical signal? supplied to various alarm devices or control devices so that a protective device, such as the automatic shut-off valve or the control device of the gas combustion appliance, is actuated thus preventing the that a fire occurs due to the earthquake.

The oscillation due to the earthquake must be distinguished from the other oscillation or disturbing oscillation to prevent unnecessary activation of the protection device when the seismic element previously described? incorporated in the automatic shut-off valve used in the town gas appliance or commercial propane gas equipment. The oscillation due to the earthquake has waveforms in a wide cycle range. A sinusoidal wave oscillation varying between 0.3 and 0.7 seconds of cycle? usually used as an alternative feature. When a field of the response threshold of the seismosensitive element? between 130 and 190 gal, which field corresponds to that of the earthquake of intensity? seismic 5, the sinusoidal oscillation with variable cycle between 0.3 and 0.7 seconds? applied to the seismosensitive element, which sinusoidal oscillation assumes a response field value in an acceleration field corresponding to the threshold field. For example, consider the case where a microcomputer? intended to determine that you? an earthquake occurred, in the condition in which signals "on? and" off? each having a period of 40 milliseconds or more? are applied for three cycles or more? within three seconds. The signal generated by the seismosensitive element must be in accordance with the previously mentioned condition so that? the microcomputer determines the appearance of the earthquake when the sinusoidal oscillation previously described? applied to the seismic-sensitive element and the protection device, such as the automatic shut-off valve, is activated.

The elasticity of the contact plate 7 and the angle 7B of the tab part 7A are important factors for determining the "on" and "off" periods of the signal in the seismosensitive element according to this embodiment. For example, consider the case where the contact plate 7? formed from a phosphor bronze plate having a thickness of 0.05 mm, a length of 4 mm and the width of each tab part? 0.5 mm and the inertial sphere 8? formed from a steel sphere of approximately 0.7 gr with nickel plating applied to it. In this case, when the angle 7B of each tab part 7A with respect to the lower face 2B? 90? and the tab portions 7A are disposed around the sphere 8 concentrically therewith, the inertial sphere 8? immediately bounced on contact with the tab part 7A and hops up and down against the lower face 2B of the casing. Consequently not? Sufficient contact duration of the inertial sphere 8 with the tab parts 7A can be achieved. What? Not ? Is it possible to obtain a necessary "on" period even when the sinusoidal oscillation having the aforementioned response range? applied to the seismosensitive element in the predetermined cycle. Furthermore, since? the "on" period? short, ? difficult to discriminate the operative characteristic of the element from that in the case in which the sinusoidal oscillation is applied in a cycle pi? short of the predetermined one. In addition, the swing can not? be distinguished from electrical noise. The phenomena previously described become more? evident when the contact plate 7 has a high elastic constant. Can you? understand that as the inertial sphere 8 rolls in response to oscillation in contact with the tab parts 7A, as illustrated by dotted lines in Figure 2, a function for maintaining the contact condition must be provided by the angle 7B of the part a tab 7A with respect to the lower face 2B of the casing.

When ? brought into contact with the tab parts 7A with a certain pressure, the angle 7B causes the inertial sphere 8 to receive a composite force which pushes it against the lower face 2B of the casing. Sliding on the tab parts 7A, the inertial sphere 8? braked by the composite force in the condition in which? held between tab parts 7A. Consequently, when the angle 7A? less than 90 ?, the period "on" pu? be made more? longer than that when the angle 7A? of 90 ?. Furthermore, since? the inertial sphere 8? retained between the tab parts 7A and the lower face 2B of the casing 2 with a predetermined force, the condition of the inertial sphere 8 in contact with the tab parts 7A and the lower face 2A can? be made stable. Furthermore, since? the inertial sphere 8? brought into contact with the tab parts 7A and the lower face 2B of the casing, sliding on them, the contact surface of the inertial sphere 8 can? be kept clean, which prevents a contact defect from occurring.

Consequently, the angle 7B between the inertial sphere 8 and the lower face 2B of the casing? set at a value less than 90? when the inertial sphere 8? brought into contact with the tab parts 7A. That is, the inertial sphere 8? interposed between the tab parts 7A of the contact plate 7 and the lower face 2B of the casing, similar to that in which? inserted a wedge. Consequently the inertial sphere 8? pushed by the tab parts 7A against the lower face 2B of the envelope, which stabilizes the inertial sphere 8 in the contact condition. Furthermore, an electrical contact resistance can? be stabilized since? the inertial sphere 8? brought into contact with the tab parts 7A and the lower face 2B of the casing, sliding on them, so as to obtain a braking effect.

According to the present invention, a deflection value of each tab part 7A of the contact plate 7? fixed to vary between 0.25 and 0.5 mm when a force corresponding to the weight of the inertial sphere 8? applied to a tab part 7A at the point of mutual contact. This determination of the deflection value of the tab part 7A can be provide a suitable value of a composite force exerted on the inertial sphere 8 by the contact plate 7 causing it to be pushed against the lower face 2B of the casing when the inertial sphere 8? in contact with the contact plate 7. This determination can? also provide a suitable value of a composite force that returns the inertial sphere 8 towards the center of the envelope 2. Furthermore, this determination can? provide a suitable value of the contact duration between the inertial sphere 8 and the tab parts 7.

The following facts were confirmed in an experiment in which an inertial sphere of steel having a? Meter of 5.5 mm and a weight of 0.7 gr? which inertial sphere 8 was used, i.e. a deflection value of the contact plate in the event of collision of the inertial sphere against this plate? small when each tab part is 0.5mm wide and 0.06mm thick or more. Is the "on period made shorter than the" off period? since? the inertial sphere? bounced off the tab parts. Furthermore, the inertial sphere cannot? accurately follow the oscillation applied to it since? its movement? disturbed when? bounced off the tab parts. Furthermore, even when the angle 7B of the tab part 7A with respect to the lower face 2B of the casing? set at a value of 90? or less, ? difficult to cause the inertial effect resulting from a holding force of the inertial sphere between the tab parts and the lower face of the casing and from the sliding movement of the inertial sphere, since? the value of each tab part? limited. In this case the "on" period of the signal is not? much increased compared to the case where the angle 7B? 90 <a>.

In case the diameter of the inertial sphere is greater than 5.5 mm, the waveforms of the signals on "and" off? may be suitable for the microcomputer determination condition even when the thickness of each tab part assumes a value of 0.06mm or more. However an inside diameter of the casing? limited when producing a small seismosensitive device. Under these conditions, when the diameter of the inertial sphere? increased, the distance of movement of the inertial sphere is reduced, which can not? provide a sufficient "off" period. So the increase in the diameter of the inertial sphere as previously described does not? advantageous.

Figure 3 represents the relationship between the inclination 2C of the lower face 2B of the casing and accelerations and frequencies, on the basis of which the microcomputer determines that yes? an earthquake occurred. The microcomputer? intended to determine that you? the earthquake occurred, under the condition that the "on" and "off" signals each having a period of 40 milliseconds or more are applied for three cycles or more within three seconds, as previously described. oscillation Fi and F2 are 1.43 and 3.3 Hz respectively, and the accelerations of oscillation Gl and G2 are 130 and 190 gal, respectively. Curves A to D show the characteristic in the case of different inclinations 2C of the lower face 2B Curve A shows the case in which the inclination 2C of the lower face 2B of the enclosure is less than 2?, the curve B the case in which the inclination 2C is 3?, the curve C the case in which the inclination? of 6 "and the curve D the case in which the inclination? of 11 ?. Can you? understand from figure 3 that the seismosensitive element also operates in a high frequency field when the inclination 2C? small, which shows that the element operates in response to the so-called noise due to a disturbing oscillation. Also, when the 2C tilt? great, the malfunction of the element in the high frequency range can? be prevented while the sensitivity? of the element? decreased in the low frequency range. What? the response characteristic of the seismic-sensitive element? decreased when the 2C inclination? large, and furthermore the oscillation acceleration to which the seismosensitive element responds in the low frequency field increases.

In the light of the foregoing discussion, the inclination 2C of the lower face 2B of the casing? fixed in the range between 4 and 10? and the inner diameter of the casing 2? fixed so that the sum of this diameter and the diameter of the inertial sphere 8 is within 4 mm, in this embodiment. Consequently you can? prevent the inertial sphere 8 from jumping vertically against the horizontal oscillation and the value of its rolling resistance can? be reduced even when using an inertial sphere pi? small in order to reduce the size of the seismosensitive element. What? ? It is possible to obtain a stable contact between the inertial sphere and the contact plate and the lower face of the casing.

Furthermore, in the event that the inclination 2C of the lower face 2B of the casing is 3 or less, a rolling friction can? prevent the inertial sphere 8 from returning to the center of the enclosure, if the seismic element 1? tilted by 1 or 2? compared to the normal trim in the installed condition. Consequentially ? high installation precision is required when the seismic element is installed. Furthermore, a composite force acts on the inertial sphere 8 pushing it against the lower face 2B of the casing while the inertial sphere 8 rolls in response to the oscillation acceleration. The contact between the inertial sphere 8 and the lower face 2B of the casing? unstable since? this composite force? insufficient. Consequently it can? vibration occur when the inertial sphere 8? brought into contact with the tab parts 7A. Also, when the 2C slope exceeds 10 ?,? It is possible to obtain a sufficient composite force which pushes the inertial sphere 8 against the bottom 2B of the casing, which stabilizes the contact between the inertial sphere 8 and the lower face 2B of the casing. However in this case the resistance value of the inertial sphere 8 varies with the increase of the rolling, which reduces the distance for which the inertial sphere 8 rolls and the distance for which the inertial sphere 8 moves, sliding on the tongue parts. 7A. The contact duration between the inertial sphere 8 and the tab parts 7A also becomes insufficient. Consequently, the ratio between the "on" period and the "off1 'period becomes large, which makes it difficult to make the output signal match the determination criterion programmed in the microcomputer.

The inner diameter of the casing 2? determined as follows. The main frequency of the earthquake varies between 1 and 5 Hz. The sinusoidal oscillation having the frequency in the range previously described as an alternative characteristic? applied to the seismic-sensitive device in a characteristic test. A stable output signal can? be obtained when the inertial sphere rolls on the lower face of the casing for a maximum distance of 2 mm from its center. The realization of a greater distance produces a redundancy and an increase in the size of the seismosensitive device.

For example the width of 6 mm? applied to the seismosensitive field when the oscillation having the frequency of 2 Hz? applied to the seismosensitive element and the acceleration? 100 gal, what? approximately its lower limit value in the case of the intensity earthquake? seismic 5. When the inertial sphere? such as to start rolling at 100 gal? its distance of movement? determined at a value of 2 mm or less from its center, the inertial sphere? brought in contact reliably with the contact plate since? rolls to its position of maximum movement.

Plus the breadth? about 2.5 mm when the oscillation frequency? 5 Hz and acceleration? 250 gal, what? approximately its higher value in the case of the intensity earthquake? seismic 5. Also in this case the inertial sphere? brought into contact with the contact plate. However in reality? a necessary distance of movement of the inertial sphere 8? of 2 mm in its response to normal oscillation since? the range of motion of the inertial sphere? reduced by its contact with the contact plate and its sliding movement. A greater distance of movement of the inertial sphere does not? necessary. Conversely, when the distance of movement of the inertial 3phere? set at a value greater than necessary, the seismic-sensitive device? subject to a? relatively large acceleration of impact during transport so the inertial sphere? made to move by colliding with the inside of the enclosure. In this case the angle 7B between the contact plate and the inertial sphere? reduced and a resistant force due to the friction induced by the inertial sphere pushed against the bottom of the casing becomes greater than a return force resulting from the weight of the inertial sphere and a repulsive force of the contact plate. Consequently there? a high possibility? that the inertial sphere is held between the bottom of the casing and the contact plate, so the inertial sphere cannot? return to its normal position even when the seismic device? returned to its normal position.

How ? obvious from the above, the maximum distance of movement of the inertial sphere 8 pu? be defined by determining the internal diameter of the casing 2. Consequently, the distance of movement of the inertial sphere 8 in the event that the seismic-sensitive device is subject to the acceleration of an abnormal impact can? be made approximately equal to that due to normal oscillation. Consequently you can? prevent the angle 7B from being unnecessarily reduced, which accentuates the return of the inertial sphere 8 under the action of its own weight and the repulsive force of the contact plate 7.

The amplitude? about 1 mm when the oscillation frequency? of 5 Hz and acceleration? of 100 gal. In this case the "on" and "off" signals are reliably generated when the distance between the inertial sphere 8 and the tab parts 7A is set at a value no greater than the amplitude. of 5 Hz, each of the signals "on? and "off? is theoretically generated ten times for one minute. The signal cycle is 50 milliseconds if the period" on? ? as long as the "off" period. However, since? the period of time of operation of the seismosensitive device in reality? varies, there? the possibility? that the frequency of 5 Hz or less cannot be detected when the microcomputer? programmed so that the determination threshold value is 50 milliseconds. Consequently, each of the "on" and "off" time periods is set at 40 milliseconds or more according to the invention, so as to allow for variations in the operating time period. determine that an earthquake has occurred when the oscillation frequency is 6.25 Hz or more.

Based on the factors previously described, the microcomputer? programmed and the distance between the inertial sphere and the contact plate, the spring constant of the contact plate, the inclination of the lower face of the casing and the like are determined.

The following problem can? be encountered when the vertical distance between the contact plate 7 and the inertial sphere 8? short. That is, in the condition that a part of the tab part 7A with which the inertial sphere 8 comes into contact does not vary, the length of the tab part 7A? made smaller in the case in which the vertical distance mentioned above is short compared to the case in which it? long. When the length of the tab part 7A? reduced, its elastic constant increases and an angular variation of the tab part 7A with respect to the entity? of the movement of the inertial sphere 8 increases. Consequently, the mass of the inertial sphere 8 must be increased or the spring constant of the contact plate must be reduced. Also, the contact angle of the inertial sphere 8 with respect to the tab part 7A? unnecessarily decreased when the inertial sphere 8 moves so as to be adjacent to the internal face of the casing 2, since? the angular variation of the tab part 7A? great. Consequently there? the possibility? that the resistive force due to friction can become greater than the return force of the inertial sphere 8 due to the repulsive force of the tab part 7A.

In light of the previous discussion, the vertical distance between the inertial sphere 8 and the contact plate 7? determined to be five percent of the diameter of the inertial sphere 8 or more. This determination gives the contact plate a desired performance without the use of the contact plate made of an unnecessarily thin material or made with an unnecessarily lean construction or without the use of the large mass inertial sphere. For example, when the inertial sphere 8 used has a diameter of 5 mm and the vertical distance between the inertial sphere 8 and the contact plate? 7? 0.5 mm, the time periods "on? And" off? they are stable in the condition in which the part of the tab part 7A with which the inertial sphere 8 comes into contact does not vary. However, both "on" and "off" time periods become non-uniform when the vertical distance is 0.2 mm. The reason is that the spring constant of the contact plate increases, as previously described. Also, according to the present invention , the permissible error at the time of assembly must not be made less than necessary, which simplifies assembly.

The sine waves are used as an alternative characteristic in the characteristic test of the seismosensitive device as previously described, since? ? difficult to reproduce the oscillation of a real earthquake. Consequently, the acceleration varies widely in the actual earthquake. varies relatively uniformly in the characteristic test. Consequently there? the possibility? what, when the seismosensitive device? subject to a particularly high acceleration of impact or oscillation, the inertial sphere 8 can enter in depth? between the tab parts 7A and the lower face 2B of the casing being held together if the friction force acting between the inertial sphere 8 and the tab parts 7A? high. In this case, the self-weight and the repulsive force of the tab parts 7A cannot bring the inertial sphere 8 back to its previous position as it becomes stationary with the disappearance of the oscillation and consequently the electrical path cannot? be open.

To overcome the disadvantage described above, the seismic-sensitive device according to the invention? constructed so that a resultant force (F4 + F5) is greater than a resultant force (F2 + F3) in the field of motion of the inertial sphere, where F2 represents a composite force of a frictional force Fi between the inertial sphere 8 and the tab part 7A, in which the composite force F2 acts in a direction parallel to the bottom of the casing, F3 represents a frictional force between the inertial sphere and the bottom of the casing, F4 represents a composite force of an applied repulsive force to the inertial sphere from the tongue part, in which the composite force F4 acts in a direction parallel to the bottom of the casing, and F5 represents a composite force due to the weight of the inertial sphere, in which the composite force F5 acts in a direction parallel to the bottom of the casing.

In the construction previously described, can you? prevent the inertial sphere 8 from being held between the tab part 7A and the bottom of the casing and it can be allowed to return to the previous position, regardless of the position that the inertial sphere can? assume within its range of motion. Consequently, the electrical path can? be reliably opened. There? sar? further described with reference to figure 4. Figure 4 represents a vector illustration of the forces acting on the inertial sphere 8 of the seismosensitive element employed in the eismosensitive device. In figure 4, the reference symbol F designates the repulsive force applied to the inertial sphere from the tongue part, W indicates the weight of the inertial sphere, P indicates the center of the inertial sphere, a indicates an inclination between the lower face of the casing and a tangent touching the inertial sphere, | 3 indicates an inclination between the tongue part and a horizontal plane, in which b> 0, ?? indicates a coefficient of friction at a point of contact between the inertial sphere and the tongue part and ?? indicates a coefficient of friction at a point of contact between the inertial sphere and the lower face of the casing. The inclination a previously mentioned? an inclination of the tangent at the point of contact between the inertial sphere and the lower face of the envelope. The inclination a corresponds to the inclination 7B when the lower face of the enclosure? conical as shown in Figure 2. However, it does not necessarily correspond with the inclination 7B when the lower face of the casing has other configurations. So that? the inertial sphere 8 returns to its previous position on the recess 2A when the seismic element? at rest in the normal state, the following expression must be satisfied:

F. sin (? +?) W. sin to> uA. F. cos (? + (3)

?? . (W. cos a F. Cos {a + |?}) (2) where a |? <900.

Describing expression (2), the left side of the expression shows the return force that causes the inertial sphere 8 to move to the right along the lower face 2B of the envelope, as 3i sees in figure 4. Its side right shows the frictional force that makes s? that the inertial sphere 8 remains in position. The inertial sphere 8 begins to move when the force represented by the left side of the expression? higher than that represented by the right side while remaining in place when the force represented by the right side of the expression? higher than that of the left side.

The left side of expression (2) includes a term representative of the return force due to the repulsive force F and a term representative of the return force due to the weight V of the inertial sphere 8. Pi? in particular, the term F. sin (? +?) represents a composite force of the repulsive force F acting in the direction parallel to the lower face 2B of the casing or the return force. The expression W.sina represents a composite force of the weight of the inertial sphere 8 acting in the direction parallel to the lower face 2B of the casing or the return force.

The right side of expression (2) includes a term representative of a composite force of the frictional force resulting from the repulsive force of the tab part 7A and the friction at the point of contact between the tab part 7A and the inertial sphere 8, which point of contact will be? referred to as "point of contact A". The right side of the expression also includes a term representative of the frictional force resulting from the force that pushes the inertial sphere 8 against the lower face 2B of the housing and from the friction at a point of contact between the inertial sphere 8 and the lower face 2B of the enclosure, which point of contact will be referred to as "contact point B". The term nA.F represents the frictional force acting in the contact point A. The term ?? - F.cos (a + |?) Represents the composite force acting in the direction parallel to the lower face 2B of the casing. The inertial sphere 8? pushed against the lower face 2B of the enclosure by a force resulting from the composite force of the weight of the inertial sphere 8 acting vertically on the lower face 2B of the enclosure and represented by the term W. what and the composite force of the repulsive force F acting vertically on the lower face 2B of the envelope and represented by the term F.cos (a + |?). This resulting force produces the frictional force represented by the term uB (V.cos? + F .cos (a + |?)).

The force of friction ?? .F due to the sliding friction at the contact point A or the frictional force ?? ^?. ??? a F.cos (a + (?)) smaller than the other causes the inertial sphere 8 to crawl, and the other frictional force does not cause the inertial sphere to crawl. Consequently the inertial sphere? rolled. For example, consider the case where the weight of the inertial sphere 8? 0.69 g when a = 6 ?, the angle |? between the tongue part in the free condition without elastic deformation produced by the inertial sphere and the inertial sphere at the point of contact? 55 ?, the angle (3 between the tongue part and the lower face of the enclosure in the position where the inertial sphere engages with the lower face of the enclosure? 40 ?, and the repulsive force F? 0,6 g Under these conditions, the frictional force at the contact point B exceeds the frictional force at the contact point A and consequently the inertial sphere crawls on the tab part and rolls along the bottom face of the housing. understand that the coefficient of friction at the contact point of the tongue part and the inertial sphere, which coefficient is represented in the right side of expression (2), represents a static coefficient of friction resistance under the conditions mentioned above and that the coefficient of friction?,? at the point of contact B of the inertial sphere and of the lower face of the casing represents a coefficient of rolling friction under the conditions mentioned above.

In general, a coefficient of friction depends on the material and the surface condition. Now consider the case in which the sliding friction coefficient between the inertial sphere and the tongue part or between the inertial sphere and the lower face of the casing? 1.0 and the rolling friction coefficient between the inertial sphere and the tongue part or between the inertial sphere and the lower face of the casing? 0.001. When these values are applied to expression (2), does it also hold when the inertial sphere? arranged in a position in which it engages with the lower face of the casing in the seismic-sensitive element under the conditions described above. So can you? understand that the weight of the inertial sphere and the repulsive force of the tab part cause the inertial sphere to roll.

There? the possibility? what a roughness? of the surfaces of the inertial sphere, the tongue part and the lower face of the housing and small cracks on these surfaces can increase the values mentioned above. In this case the inertial sphere will be? retained between the lower face of the housing and the tab parts after which? rolled, and consequently the inertial sphere cannot? return to the previous position. However in reality? the elastic constant of the tab part and the like are fixed so that the inertial sphere cannot engage with the inner wall of the casing in the seismic-sensitive element previously described when? subject to normal swing acceleration. Even when the element? subject to an impulsive acceleration greater than the normal oscillation acceleration, for example, one cannot? consider that no reaction is produced in the position where the inertial sphere engages with the inner wall of the envelope.

However the inertial sphere moves easily engaging with the inner wall of the casing when the free angle (? Of the tongue part is small. Consequently the inertial sphere will be held by the frictional force when the coefficient of friction is high. the distal end of the tab part touches the inertial sphere or the inner wall of the enclosure when the free angle is excessively large, and consequently the electrical path will not be open.

In light of the previous discussion, the free angle? 0? determined to vary between 45? and 75 "e? + fl J> 40?, where a represents an inclination of the tangent at the point of contact between the inertial sphere and the lower face of the envelope when the inertial sphere engages the lower face of the envelope and the inner wall of the casing simultaneously and (5 represents an inclination of the tab part with respect to the horizontal plane, where a> 0 and (3> 0. The inertial sphere can be prevented from being held between the tab parts and the lower face of the casing when the corners of the tab part 7A in its free condition and in its condition of maximum elastic deformation are fixed as described above.

So that? ? +? > 40 "when f30 is set at 40" or less, the repulsive force for the return of the inertial sphere cannot be obtained since the elastic deformation of the contact plate produced by the inertial sphere cannot be obtained. Consequently the constant In this case, the elasticity of the contact plate must be increased. In addition, the variations in the duration of contact of the inertial sphere increase as the distance over which the inertial sphere moves by sliding on the contact plane is reduced. selection of the length of the tab part is reduced in order to prevent the distal end of the tab part from touching the inertial sphere or the inner side wall of the housing when it is set at 75 ° or more. distal end of the tab portion engages with the inner sidewall of the envelope before the inertial sphere engages with it, when the length of the tab portion is fixed to gives such a large value that the point of contact of the contact plate with the inertial sphere is not? placed on the end? distal of the tab part. On the other hand, the extremity? distal of the tongue part engages with the inertial sphere when the tongue part? made short in order to prevent that the end? distal of the tab part touches the inner sidewall of the envelope. Consequently, the dimensional tolerance and erection tolerance of the tab part as a component are restricted, which requires high precision in manufacturing the component.

Also, when the value of? +? ? 40? or not, the force that pushes the inertial sphere against the lower face of the envelope, which force? a composite force of the repulsive force of the tongue part against the inertial sphere,? increased <'> when the inertial sphere engages with the inner side wall of the enclosure. The frictional force acting on the inertial sphere exceeds the force. of recall of the inertial sphere and consequently the inertial sphere? held between the contact plate and the lower face of the enclosure.

In light of the previous discussion, when the inclination (30 of the tongue part with respect to the horizontal plane is set to a value less than 75 °, as previously described, it is possible to prevent the distance that the inertial sphere moves by sliding on the plate of contact is shortened and it is possible to ensure a sufficient setting of the dimensions of the tab part, which makes assembly easy. tongue of the contact plate even when the inertial sphere occupies the position in which it engages with the inner side wall of the enclosure.

Figures 5 and 6 illustrate the previously described seismosensitive element enclosed in a resin casing 12 containing the element in its normal position. An electrically conductive L-shaped plug 13? welded on the head 4 of the seismic-sensitive element 1. The seismic-sensitive element 1? inserted into the casing 12 through its lower opening. Terminal plug 6 and plug 13 are inserted through openings 12A and 12B formed in housing 13, respectively. The head 4? in engagement with a protruding part 12C for maintaining the attitude formed inside the casing 12 so that the seismic-sensitive element 1 is positioned. In this condition, terminals 14 and 15 are welded at the ends? of the terminal plug 6 and of the plug 13 protruding from an upper part of the casing 12, respectively, so that the seismic-sensitive element 1 is fixed to the casing 12.

So that? the seismosensib device? le 11 is mounted, for example, on a Kerosene fan room heater, the lower face 12D of the casing 12? firmly fixed to a lower plate of the space heater or the like and then screws are inserted into respective fixing openings 12E to be screwed so that the seismic-sensitive device is fixed.

Figure 7 illustrates a second embodiment of the invention. In the second embodiment, a protection element 9 having a high stiffness? arranged in the vicinity of the part of the contact plate 7 fixed to the terminal pin 6 so as to be able to avoid a permanent deformation of the contact plate 7 due to the collision of the inertial sphere 8 with it. The protection element 9? formed by a sheet of steel having a thickness equal to several times that of the contact plate 7 or more. A corner 9B of a circumferential edge part 9A of the protection element 9? fixed at a value equal to or less than the angle 7B of the contact plate 7. The protection element 9? bent outward approaching its end? so that you can prevent its end? impacts against the inertial sphere 8. The dotted line in figure 7 shows the position of the inertial sphere 8 when the seismic device? subject to the acceleration of oscillation. How ? obvious from this position of the inertial sphere 8, the protection element 9? mounted so as not to obstruct the normal movement of the inertial sphere 8 and the normal elastic deformation of the tab parts 7A of the contact plate 7 when the seismic-sensitive device? subject to normal swing acceleration under normal operating condition.

The contact plate 7 will be? retained between the inertial sphere 8 and the protection element 9 when the seismic-sensitive device? subject to large acceleration, such as impact acceleration. However, the shape of the protective element 9? determined so that the deformation of the contact plate 7 does not exceed its elastic deformation range when the contact plate 7? retained between the protection element 9 and the inertial sphere 8. Furthermore, the protection element 9? made in such a way as to have no angle that holds the contact plate 7 with the inertial sphere 8. What? permanent deformation of the contact plate is prevented.

Figure 8 illustrates a third embodiment of the invention. In the third embodiment, a protection element 10? arranged between the contact plate 7 and the inertial sphere 8 so as to be able to prevent the contact plate 7 from being held between the inertial sphere 8 and the protection element 10. The protection element 10 is not? brought into contact with the inertial sphere 8 during its rolling on the lower face 2B of the casing in the condition in which the seismic-sensitive element 1? subject to normal acceleration in its normal operation, as indicated by dashed lines in Figure 8.

The inertial sphere 8 collides with the protection element 10 when the seismic-sensitive device? subject to the acceleration of impact or the like so that the inertial sphere 8 moves upwards, as seen in figure 8. In this case the direct collision of the contact plate 7 with the inertial sphere 8 can? be avoided as in the second embodiment, so as to be able to prevent permanent deformation of the contact plate 7.

Figure 9 illustrates a fourth embodiment. In the seismic-sensitive element 10, the casing 2 containing the electrically conductive inertial sphere 8? closed by the head 3 in the same way as in the first embodiment so as to form the closed envelope. The angle between the lower face 2B of the casing and the tab part 17A of the contact plate 17 which acts as the contact part with the inertial sphere 8? about 90 ?. The length of the tab part 17A? determined so that its extremity? distal is disposed more? at the bottom of the plane passing through the center of the inertial sphere 8.

The deflection value of the tab part 17A? fixed so as to be included in the range between 0.25 and 5 mm when the force corresponding to the weight of the inertial sphere 8? applied to a tab portion 17A at the point of contact of the tab portion and the inertial sphere, as previously described. This determination of the deflection value of the tab portion 17A can allow the tab portion 17A to flex and provide a stable signal. When is the deflection value of the tab part 17A? less than 0.25mm, the contact time period of the tab part 17A and the inertial sphere 8 becomes too short and the signal becomes unstable. When the deflection value exceeds 5 mm, the contact time period becomes too long, which makes it difficult to distinguish the frequency-dependent variation of the cadence of "on" and "off" periods.

However, in this embodiment the tab portion 17A flexes when the inertial sphere 8 collides with it how? indicated by dotted lines in Figure 9. The inertial sphere 8? decelerated by the bending of the tab portion 17A. Furthermore, since? the tab part 17A? inclined towards the outside at the collision of the inertial sphere 8 with it, the composite force that pushes the inertial sphere 8 against the lower face 2B of the casing? applied to the inertial sphere in the same way as in the case where the tongue part? originally formed to be tilted outward, as shown in Figure 1 and, consequently, the inertial sphere 8? decelerated by its sliding motion.

Figures 10 and 11 illustrate a fifth embodiment. Also in the seismosensitive element 18, the casing 2 which encloses the electrically conductive inertial sphere 8? closed by the head 3 in the same way as in the previous embodiments so as to obtain the closed envelope. The contact plate 19 fixed at the end? distal of the terminal pin 6 comprises the tab parts 19A starting with a horizontal part 19B. Does a part bent down 19E have an end? distal 19C intended to be disposed more? above the center of the inertial sphere 8. E? it is preferable that the angle between the tab part 19A and the lower face 2B of the casing is 90? or less. A bent part 19D of the tab part 19A? provided to avoid the intrusion of the tab part 19A into the inertial sphere 8 at the moment of engagement.

In the fourth embodiment illustrated in Figure 9, a force acting so that the inertial sphere 8 is damped by the tab parts 17A? produced when the spring constant of the tab part 17A? high and the angle between the tongue part 17A and the lower face 2B of the casing? 90? or more. Consequently, the contact of the inertial sphere 8 with the lower face 2B of the casing becomes unstable.

However, in the fifth embodiment the extremity? distal 19C of the tab part 19A? willing more? at the top with respect to the center of the inertial sphere 8. With respect to the construction in which the extremity? distal of the tongue part not? willing more? above the center of the inertial sphere, the movement distance of the inertial sphere moving until it engages with the tab part 19A? major, how? obvious from the position of the inertial sphere indicated with dashed lines in figure 10. Consequently, the diameter of the contact plate can? be reduced with respect to the inertial sphere 8 and consequently the seismosensitive element can? be made small. Furthermore, since? the tab part engages with the inertial sphere at its part above its center and the tab part 19A begins with its horizontal part 19B, the contact plate 19 flexes upward to its engagement with the ball inertial regardless of the angle between the tongue part and the lower face of the enclosure. Consequently, the force is produced which pushes the inertial sphere 8 against the lower face 2B of the casing and stabilizes the contact between the inertial sphere 8 and the lower face 2B of the casing. Furthermore, since? the inertial sphere 8 engages with the tab part 19A at its part above its center, the force which acts so that the inertial sphere 8 3 is taken up by the tab parts 19A not? produced even when the angle of the tab part 19A with respect to the lower face 2B of the casing? 90 "or more. Consequently, the contact between the inertial sphere 8 and the lower face 2B of the housing can be stabilized even when the bend angle of the tab portion 19A is 90" or more.

Figure 12 illustrates a sixth embodiment. The contact plate 20 of the seismosensitive element? formed by a thin metal sheet. The contact plate 20 has two tab portions 20A extending from its portion attached to the terminal pin 6. Each tab portion 20A has an arc-shaped contact portion 20B at its end. protruding. The contact parts 20B are arranged so as to circle the inertial sphere 8 in a circular form. Consequently, the inertial sphere 8? brought into contact with the circular contact parts 20B when the seismosensitive element? subject to acceleration.

Figure 13 illustrates a seventh embodiment. The seismic-sensitive device 21 comprises a casing 23 comprising a housing 22A made of a resin and a head 22B fixed to the housing 22A by ultrasonic welding and the seismosensitive element 1 enclosed in the casing 23. A hook 24 which acts as a suspension part? fixed to the terminal plug 6. The casing 23 serves to keep the seismosensitive element 1 in its normal position. Terminals 25A and 25B are fixed to the housing 22A through insert molding to electrically connect the inside of the enclosure 23 and its exterior. One extremity? of hook 24? suspended on a support 26 arranged in the housing 22A so that the seismosensitive element 1 is supported in an oscillating way and the gravity? causes the seismic-sensitive element 1 to assume its normal position.

A certain amount? of a liquid 27 having a viscosity? selected, such as silicone oil,? enclosed in housing 22A. A common thread 28? connected to an end? to the metal plate 4 which is at the same potential as the casing 2 of the seismosensitive element 1 and? also connected to the other end? to terminal 25A. Another common thread 29? connected to an end? to the terminal plug 6 which is at the same potential as the contact plate 7 and? also connected to terminal 25B.

Sar? now described the operation of the seismosensitive device 21. And? a high level of precision is required in the assembly of the seismosensitive device 11 illustrated in Figures 5, 6. For example, the activation value of the seismosensitive device? reduced by about 20 gal when? mounted only with an inclination of one degree. In the seventh embodiment, on the other hand, the seismic-sensitive element 1? supported in an oscillating manner on the support 26 so that the position of the seismic-sensitive element 1 is automatically compensated for by gravity? so that the element assumes its normal position, when its mounting angle is within an allowable inclination or in a free space in which the element 1 can? assume the normal position in the volume of the envelope 23. The viscosity? of the liquid 27? selected so that the seismic-sensitive element 1 assumes its normal position within a predetermined period of time, for example 20 seconds after the enclosure 23? inclined.

When is the seismosensitive element 1 mounted as previously described? subject to oscillation or acceleration, the seismosensitive element 1 responds, integrally with the envelope 23, to the oscillation with a cycle of 2-3 seconds, for example, since? the liquid 27 with the viscosity? selected? contained in the envelope 23, and there? can provide reliable detection.

The seismic-sensitive device? been recently mounted on a gas meter with an automatic shut-off valve for town gas? or commercial propane gas equipment. The body of a person passing by the gas meter or an object carried by that person can? bumping into the gas meter or a game ball can bump against the gas meter since? the gas meter? usually placed outside. In that case there? the possibility? that the seismic-sensitive element is subject to an oscillation of noise. An experiment performed by the inventors shows that an? Oscillation acceleration of the sine wave form? applied to the gas meter when the gas meter? subject to a disturbing oscillation as previously described. In this case, the oscillation acceleration decreases from about 1000 gal in the cycle by about 0.1 seconds, even though the cycle differs more? or not due to the gap between the supporting positions of the metal brackets. Now suppose that the threshold of the seismosensitive device is fixed at 150 gal and that the microcomputer is programmed to determine that yes? an earthquake occurred when the "on" and "off" signals each having a period of 40 milliseconds are generated in three cycles or more? within three seconds. In this case the period of the "on" and "off" signals becomes 40 milliseconds even when the seismic-sensitive device generates the "on" and "off" signals each having a period of 25 milliseconds. Consequently, the microcomputer does not determine that it is An earthquake occurred.

The seismic-sensitive device? put into operation when an equipment on which the seismosensitive device? when mounted, it overturns or tilts when an earthquake occurs before the seismic-sensitive device responds to the oscillation acceleration. When the activation condition continues for a second or more, the same determination is made as in the case of an earthquake having a predetermined acceleration. When is the inclination? for example of 5? in accordance with the free volume in the envelope 23, the seismic-sensitive element 1 rapidly assumes its normal position and the inclined condition of the seismic-sensitive device cannot? be detected when the liquid 27 does not? contained in the casing 23. When the liquid 27? contained in the casing 23, the seismosensitive element 1? curbed by viscosity? of the liquid 27 so that the seismic-sensitive element 1 gradually returns to its normal position within the predetermined period of time, for example within 20 seconds, after an abrupt inclination of the seismic-sensitive device. Since? the on period of the signal becomes one second or more, the microcomputer can determine that the equipment on which the seismic sensitive device is mounted has been tilted. Consequently, it is possible to provide an alarm or control controlled equipment.

In each of the foregoing embodiments, the recess 2A? arranged as a resting part for the inertial sphere in the bottom of the casing of the seismic-sensitive element. However, the rest part can? be eliminated according to the working conditions of the seismic-sensitive element, as shown in figure 14.

Figures 15 to 17 illustrate modified forms of the contact plate. In the contact plate 30 shown in FIG. 15, each tab portion 30A has an end. distal curved outward. In the contact plate 31 illustrated in FIG. 16, each tab portion 31A has a greater width at its root portion than at any other portion thereof because tension concentrates on the root part. In the contact plate 32 shown in FIG. 17, each tab portion 32A has a greater width at its end. distal to any other part thereof so that the contact between the inertial sphere and the contact plate is stabilized.

Figures 18 and 19 illustrate an eighth embodiment. The invention? applied to a tilt switch in the eighth embodiment. A tilt switch 41 includes a housing 43 and a head 42 welded to the housing 43. The head 42? formed from a substantially circular metal sheet 44 and has a through opening 44A formed in its central part. The conductive terminal plug 45? inserted through opening 44A so as to be secured therein by the electrically insulating filling material 46, such as glass or ceramic.

The contact plate 47 made of the electrically conductive material? welded at the end? distal of the terminal plug 45 on the inside of the housing. The contact plate 47? arranged in a substantially concentric position with respect to the terminal plug 45. The contact plate 47 has a multiplicity of characteristics. of parts to tongue 47A with an elasticit? enough. When the contact plate 47? made of phosphor bronze and a conductive sphere has the mass of 0.7 g, a suitable thickness of the contact plate 47? within the range of 0.01 to 0.03mm and a suitable width of each tab part 47A? about 0.5 mm. A protection member 48 made of a metal having a high stiffness? fixed on the side of the contact plate 47 opposite to that fixed to the terminal pin 45 in order to prevent permanent deformation of the contact plate 47 due to the collision of the conductive sphere 49 with it.

The casing 43? made of a conductive material, such as a metal, in a cylindrical shape and has a bottom. Is the neutral holding part or a neutral recess? formed in the central portion of the bottom of the casing 43. The bottom of the casing 43 has a neutral position holding part or a neutral recess 43A formed in its central part and a rolling face 43B around the neutral recess 43A so that the bottom of the casing is made in the form of a shelf. The rolling face 43B? formed as an inclined face that rises radially from the central part. The part of the inclined face on which the conductive sphere rolls has a greater inclination on the radially central side and a minor inclination on the external side so that the inclination varies continuously. or in a discontinuous way. The massive conductive sphere 49 made of a metal or similar? arranged in the casing so as to be positioned in correspondence with the central neutral recess 43A by the action of gravity while the tilt switch assumes its normal position and the conductive sphere 49? at rest.

Sar? The operation of the tilt switch 41 is now described. A fixed operating angle for the tilt switch 41 depends on a contact angle a between the conductive ball 49 and a free edge 43E of the recess 43A. The contact angle al depends on the diameter di of the contact part between the conductive sphere 49 and the free edge 43E and on the diameter d2 of the conductive sphere 49. The contact angle al? 35? in this embodiment. When the tilt switch 41 assumes the normal position, the conductive ball 49.? maintained at the free edge 43E of the neutral recess 43A where not? in contact with the contact plate 47 and the protection element 48 and does not close an electrical circuit.

The conductive sphere 49? maintained at the free edge 43E of the neutral recess 43A until its inclination reaches the fixed operating angle even when the inclination switch 41 tilts. The conductive ball 49 begins to roll when the tilt exceeds an actuation contact angle, 35? in this embodiment. Since? the inclination of the rolling face 43B moving away from the free edge 43E? varied as previously described, the inclination of the rolling face 43B with respect to the horizontal face decreases as the rolling face 43B moves away radially from the center when? the fixed actuation angle has been reached. As a result, the conductive ball 49 rapidly moves along the rolling face 43B radially to the position indicated by dashed lines in FIG. 18 once it has started rolling. When it reaches position 49A, the conductive sphere 49? brought into contact with the tab portions 47A of the contact plate 47, thus closing an electrical path between the casing 43 and the terminal plug 45. The conductive sphere 49? stabilized at the neutral recess 43A with the free edge 43E when the inclination switch assumes the normal position and? further stabilized in a position 43F where the inclination of the rolling face 43B with respect to the horizontal face decreases rapidly, when the tilt switch? inclined angle of the set actuation angle or more. The conductive sphere 49 does not? stabilized in no position on the 43D rolling face between these points. Consequently, the switching from contact to separation between the conductive sphere 49 and the contact plate 47? produced as the conductive sphere 49 rolls between the two points previously described, so that the conductive sphere 49 passes rapidly past the switching point even when a controlled equipment? slowly inclined. Consequentially ? It is possible to prevent an unstable contact condition due to an irregular movement of the conductive ball 49 near the fixed actuation angle of the tilt switch, and this is the case. can ensure a reliable "on" signal.

If both the conductive sphere 49 and the contact plate 47 were rigid bodies, these elements would repel each other immediately after the contact of the conductive sphere with the contact plate 47. As a result, a vibration occurs between the conductive sphere 49 and the contact plate 47. There? poses a problem in actual use of the tilt switch. However, according to the present invention the conductive sphere 49 comes into contact with the tab parts 47A each having the elasticity. sufficient sliding on them, so that the kinetic energy of the conductive sphere 49 is absorbed by the contact plate 47. Consequently, the vibration due to the repulsion between the conductive sphere 49 and the contact plate 47 can? be prevented. In accordance with experiments performed by the inventors,? required not less than 1 millisecond so that? the "off" condition is completely transformed into the "on" condition when the conductive sphere 49 has the mass of 0.7 g and a phosphor bronze plate used for the tab parts of the contact plate 47 is 0.015 mm thick and the 0.5 mm wide On the other hand several milliseconds are required when the contact plate has a thickness of 0.2 mm and consequently has a high stiffness.

The contact of the conductive ball 49 with the contact plate 47? held until a fixed return angle is reached. The conductive ball 49 begins rolling again when the angle of the tilt switch exceeds the fixed return angle. In contrast to the "on" operation, the inclination of the rolling face 43B with respect to the horizontal plane decreases as the rolling face 43B approaches the center of the casing bottom. Consequently, the conductive sphere 49 quickly returns to the neutral recess 43A and reliably separates from contact with the contact plate 47, returning to its initial condition at an irreversible point.

In the construction according to which the conductive sphere 49? retained on the free edge 43A of the recess 43A without contact with the bottom of the recess 43E, as previously described, a holding angle (3 between the free edge 43E and the conductive ball 49 must be acute when setting a large actuation angle. , it can be considered that the conductive sphere 49 is held by the free edge 43E when the holding angle (3 exceeds a predetermined value and that variations of the angle for which the conductive sphere 49 starts rolling are produced or the conductive sphere 49 becomes inactive The tilt switch illustrated as the ninth embodiment in FIG. 20 solves this problem.

In the tilt switch 51 shown in FIG. 20, the neutral recess 53A? formed in such a way that the conductive sphere 49 cannot come into contact with the entire free edge 53E of the recess 53A at the same time and rests in an oscillating manner against the internal bottom of the recess 53A.

Sar? The operation of the tilt switch 51 is now described. With reference to Figure 21, the actuation angle of the switch 51 depends on the contact angle a2 of the conductive sphere at the point of contact of the free edge 53E with the conductive sphere 49 , in which the reference symbol h refers to the height from the bottom of the neutral recess 53A to the point of contact of the free edge 53E with the conductive sphere 9. The contact angle a2 depends on the diameter d of the conductive sphere 49. In this embodiment, the contact angle a2? 65 "when the tilt switch is in the normal position. When the tilt switch is in the normal position, the conductive ball 49 can roll until it contacts the bottom of the recess 53A. conductive ball 49 is fixed so that it does not come into contact with the contact plate 47 or the protection member 48.

At the tilt of the tilt switch 51, the gravity? causes the conductive sphere 49 to move in the neutral recess 53E so as to contact a part of the free edge 53E. The conductive ball 49 remains in this position until the tilt of the tilt switch 51 reaches the fixed operating angle. When the tilt of the tilt switch 51 exceeds the fixed actuation angle, the conductive ball 49 passes over the free edge 53E of the neutral recess 53A and then moves rapidly on the rolling face 53B to the position indicated by the dotted line in the 21, so that the conductive ball 49 contacts the contact plate 47 closing the electrical path between the casing 53 and the terminal plug 45. Consequently,? It is possible to prevent the unstable contact condition due to an irregular movement of the conductive ball 49 near the fixed operating angle of the tilt switch as in the tilt switch 41 previously described and? It is possible to ensure the generation of a reliable "on" signal.

Also, a play is left between the conductive ball 49 and the free edge 53E of the neutral recess 53A when it occupies the central portion of the bottom of the neutral recess 53A while the tilt switch is in its normal position. Consequently, the holding angle (? Between the conductive sphere 49 and the free edge 53E is increased in the tilt switch 51 compared to the switch 41 which is set at the same operating angle as the switch 51 and in which the ball conductive 49 is held by the entire free edge 53E of the neutral recess 53A. Thus the restraining force against the conductive sphere 49 is reduced, which can keep the operating angle stable. Also it can be prevented from the conductive sphere 49 is retained in the recess 53A since the holding angle [3 is also large in the tilt switch having a large actuation angle.

In the inclination switches as described above, the conductive ball rests on the substantially central part of the contact plate 7 out of contact with the casing when the inclination switch? tilted by 180? compared to the normal position or? inverted. Consequently, there? the possibility? that the signal? on? can not be generated even when the controlled equipment? overturned.

A tenth embodiment illustrated in Figures 22 and 23? directed to a solution of the problem previously described. A ledge 78? fixed on the central part of the protection element 48, how? shown in FIG. 23. The dimensions of the protrusion 78 are fixed so that it does not fit. engage with the conductive sphere 49 even when the latter? at rest while the tilt switch is in its normal position and when the ball rolls normally. Ledge 78 can be formed integrally with the contact plate 47 or with the protection member 48.

The tilt switch 71 provided with the protrusion 78 operates in the same way as the tilt switches previously described, when does it assume the normal position and when? normally tilted or inverted. When the housing of the tilt switch 71? inverted, the conductive sphere 49 undergoes, from the projection 78, a composite force acting outwardly from the center so that the conductive sphere 49 moves on the tab portions 47A of the contact plate 47 and comes into contact with the inner wall of the ? casing 73. Consequently, the signal? on? can be reliably generated even when the switch casing? inverted.

In the foregoing embodiments, the conductive ball is prevented from rolling by the free edge of the neutral recess until the tilt of the tilt switch reaches the predetermined angle. The shape of the bottom of the casing can? be deformed in those illustrated in figures 24 to 26, provided? the conductive sphere comes into contact with. the contact plate when the operating angle of the tilt switch is reached. The bottom of the casing 83 illustrated in FIG. 24 has a concave curved face with a radius of curvature greater than that of the conductive sphere 49, and the rolling face 83B continuing from the concave curved face? made as a convex curvature face with a radius of curvature greater than that of the conductive sphere 49.

Figure 25 shows the neutral recess 93A having a bottom made as a conical face. In Figure 26, a linear face? disposed discontinuously between the neutral recess 103A and the rolling face.

Figure 27 illustrates an eleventh embodiment of the invention. In the tilt switch 111 illustrated in FIG. 27, the head 116 of the enclosure 113? made of an electrically insulating material and the terminal plug 45? fixed directly in the opening of the head 116. According to this construction, the terminal plug 45? fixed directly in the head 116 substantially in the electrically isolated condition. Furthermore, since? the casing 113? made of metal and electrically conductive inorganic material, such as glass or ceramic,? It is possible to prevent the generation of an organic contaminant which could cause an interruption of the electrical conduction between the contacts compared to the case in which the casing was made of a synthetic resin. Furthermore, the casing 113? pi? rigid and has a better cost / performance ratio than that made only in glass or ceramic.

The foregoing description and drawings are purely illustrative of the principles of the present invention and are not to be interpreted in a limiting sense. The only limitation is to be determined by the scope of the appended claims.

Claims (33)

CLAIMS 1. Acceleration-sensitive device which includes an earthquake-sensitive element comprising: a) an enclosure made of an electrically conductive material and having a bottom and one end. open, in which the envelope has an inclined face formed on its bottom so as to gently rise concentrically outwards substantially from the center of its bottom; b) a head fixed to the casing in order to close its end? open and having a through opening in which an electrically conductive terminal plug? fixed in an isolation relationship with the headboard; c) a contact member made of an electrically conductive material and fixed at one end? of the terminal plug arranged inside the casing, in which the contact member has a multiplicity? of tab portions comprising respective contact portions disposed concentrically with the terminal pin, wherein the tab portions have an elasticity. predetermined-, d) an inertial sphere enclosed in the casing so as to be substantially disposed at the center of the casing in its normal attitude in a stationary condition, in which the inertial sphere moves when? subject to oscillation, so that the inertial sphere crawls on the tongue parts of the contact member except the ends? of the tab parts so that the inertial sphere closes an electrical path between the contact member and the casing and so that the tab parts are elastically deformed, thus receiving? a force that causes it to push against the bottom of the casing. 2. Acceleration sensitive device according to claim 1, wherein a rebound force based on a resultant force (F2 + F3) of a composite force (F2) of a frictional force (Fi) between the inertial sphere and the parts in a field of motion of the inertial sphere, which composite force (F2) acts in a direction parallel to the bottom of the shell, and of a frictional force (F3) between the inertial sphere and the bottom of the shell,? fixed to be less than a resultant force (F4 + F5) of a composite force (F4) of a repulsive force applied to the inertial sphere by the tab parts of the contact member, which composite force (F4) acts in a direction parallel to the bottom of the enclosure. 3. Acceleration sensitive device comprising: a) a casing made of an electrically conductive material and having a bottom and an end? open, in which the casing has a central neutral recess in the bottom and a rolling face around the recess so that the bottom is made in the form of a shelf; b) a head fixed to the casing in order to close its end? open and having a through opening in which an electrically conductive terminal plug? fixed in an isolation relationship with the headboard; c) a contact member made of an electrically conductive material and fixed at one end? the terminal plug disposed within the enclosure, wherein the contact member has a contact part disposed concentrically with the terminal plug; And d) an inertial sphere enclosed in the casing so as to be arranged in correspondence with the recess of the bottom of the casing in its normal attitude in a stationary condition due to gravity. so as to prevent the inertial sphere from being brought into contact with the contact member, wherein the rolling face of the casing bottom? made in such a way that this face rises concentrically outwards from the center of its bottom and so that a gradient thereof decreases, in which the rolling of the inertial sphere on the rolling face of the bottom of the casing is prevented by its neutral recess until the wrapper does not? inclined by a predetermined angle, thus preventing it from coming into contact with the contact member, in which the inertial sphere can? move away from the neutral recess thus rolling on the rolling face when the casing? inclined for more? of the predetermined angle, so that the inertial sphere is brought into contact with the contact member, thus electrically connecting the contact member to the casing. 4. Acceleration sensitive device according to claim 3, wherein the contact member has a multiplicity of properties. of tongue parts having an elasticity? predetermined. An acceleration sensitive device according to claim 2, wherein the contact member? brought into contact with the inertial sphere except one of its extremities? distal. 6. An acceleration sensitive device according to claim 3, wherein the neutral recess is of a size such that the inertial sphere can roll on the bottom of the enclosure in a field defined by a peripheral wall of the neutral recess in the normal condition of the inertial sphere. . 7. An acceleration sensitive device according to claim 1, wherein a deflection value of each tab portion of the contact member? fixed in a range between 0.25 and 5 mm when a force corresponding to the weight of the inertial sphere? applied to a point of contact of each tongue part with the inertial sphere. 8. An acceleration sensitive device according to claim 2, wherein a deflection value of each tab portion of the contact member? fixed in a range between 0.25 and 5 mm when a force corresponding to the weight of the inertial sphere? applied to a point of contact of each tongue part with the inertial sphere. 9. An acceleration sensitive device according to claim 1, wherein an inside diameter of the housing? less than a sum value of the diameter of the inertial sphere and 4 mm, and an inclination of the bottom of the casing varies between 4 and 10? . 10. An acceleration sensitive device according to claim 2, wherein an inside diameter of the housing? less than a sum value of the diameter of the inertial sphere and 4 mm, and an inclination of the bottom of the casing varies between 4 and 10? . 11. Acceleration sensitive device according to claim 1, wherein 45? <(? <75? Wherein | ?? represents an angle of a horizontal plane and a part of the inertial sphere where this is in contact with the tab part of the contact member in its free condition, and? + (3> 40? where a represents an angle of the bottom of the casing with respect to the horizontal plane and (? represents an inclination of the contact member with respect to the horizontal plane. 12. Acceleration sensitive device according to claim 2, wherein 45? <? <75e wherein f30 represents an angle of a horizontal plane and a part of the inertial sphere where this? in contact with the tongue part of the contact member in its free condition, and a + (3> 40? in which ot represents an angle of the bottom of the casing with respect to the horizontal plane and (5 an inclination of the contact member with respect to the horizontal plane. 13. An acceleration sensitive device according to claim 1, wherein the bottom of the casing has a hollow central part of rest where the inertial sphere? at rest in its normal position to be held in position by gravity? and the inertial sphere moves away from the resting part when? subject to an oscillation with a predetermined acceleration. 14. An acceleration sensitive device according to claim 2, wherein the bottom of the casing has a hollow central part of rest where the inertial sphere is? at rest in its normal position to be held in position by gravity? and the inertial sphere moves away from the rest part when? subject to an oscillation with a predetermined acceleration. An acceleration sensitive device according to claim 13, wherein the rest part has a radius of between 0.1 and 0.25 times the radius of the inertial sphere. An acceleration sensitive device according to claim 14, wherein the rest part has a radius of between 0.1 and 0.25 times the radius of the inertial sphere. 17. An acceleration-sensitive device according to claim 1, further comprising a protective element disposed in proximity to a portion of the terminal pin where the contact member? fixed and having a predetermined stiffness to prevent permanent deformation of the contact member due to collision with the inertial sphere. 18. An acceleration-responsive device according to claim 2, further comprising a protection element disposed in proximity to a portion of the terminal pin where the contact member is? fixed and having a predetermined stiffness to prevent permanent deformation of the contact member due to collision with the inertial sphere. 19. An acceleration sensitive device according to claim 3, further comprising a protective element disposed in proximity to a portion of the terminal pin where the contact member is? fixed and having a predetermined stiffness to prevent permanent deformation of the contact member due to collision with the inertial sphere. 20. Acceleration sensitive device according to claim 1, wherein a surface treatment? applied to a surface of the inertial sphere, at least a part of both the contact member and the internal surface of the casing with which the inertial sphere comes into contact, to prevent conductivity? of the inertial sphere and of the part of both the contact member and the internal surface of the casing is damaged by an atmosphere in which the device? used. 21. Acceleration sensitive device according to claim 2, wherein a surface treatment? applied to a surface of the inertial sphere, at least a part of both the contact member and the internal surface of the casing with which the inertial sphere comes into contact, to prevent conductivity? of the inertial sphere and of the part of both the contact member and the internal surface of the enclosure is damaged by an atmosphere in which the device? used. 23. Acceleration sensitive device according to claim 3, wherein a surface treatment? applied to a surface of the inertial sphere, at least a part of both the contact member and the internal surface of the casing with which the inertial sphere comes into contact, to prevent the conductivity? of the inertial sphere and of the part of both the contact member and the internal surface of the casing is damaged by an atmosphere in which the device? used. An acceleration sensitive device according to claim 1, wherein the head seals the housing. 24. Acceleration sensitive device according to claim 2, wherein the head seals the enclosure. 25. An acceleration sensitive device according to claim 3, wherein the head seals the enclosure. 26. Acceleration sensitive device according to claim 1, wherein the cylinder head seals the housing and an anti-pollution gas? contained in the sealed enclosure. 27. Acceleration sensitive device according to claim 2, wherein the cylinder head seals the enclosure and an anti-pollution gas? contained in the sealed enclosure. 28. An acceleration sensitive device according to claim 3, wherein the head seals the housing and an anti-pollution gas? contained in the sealed enclosure. 29. Acceleration-sensitive device according to claim 23, further comprising a suspension member disposed outside the device, a support which supports the suspension member in a predetermined position and a body which encloses an enclosure sealed with a liquid having a viscosity? prefixed and in which the body? mounted in such a way as to be able to move in a predetermined permissible angle of inclination so that the sealed enclosure is made to assume by gravity. the normal attitude and the inertial sphere in the sealed envelope rolls when the body? subject to an acceleration due to oscillation, thus interrupting? an electrical path. 30. Acceleration-sensitive device according to claim 24, further comprising a suspension member disposed outside the device, a support which supports the suspension member in a predetermined position and a body which encloses an enclosure sealed with a liquid having a viscosity? prefixed and in which the body? mounted in such a way as to be able to move in a predetermined admissible angle of inclination so that the sealed enclosure is made to assume by gravity? the normal attitude and the inertial sphere in the sealed enclosure rolls when the body? subject to an acceleration due to oscillation, thus interrupting? an electrical path. 31. An acceleration sensitive device according to claim 4, wherein the contact member? brought into contact with the inertial sphere except one of its extremities? distal. 32. Acceleration-sensitive device according to claim 1, wherein the seismic-sensitive element generates a signal when? subject to an oscillation due to an earthquake and the device sensitive to acceleration? connected to a microprocessor provided with data relating to a cycle and a response threshold value in an alternative characteristic of an oscillation due to an earthquake of an intensity? predetermined seismic, the microprocessor being programmed to compare the signal generated by the seismosensitive element with the data, in such a way that the oscillation due to the earthquake is distinguished from a disturbing oscillation so that? the microprocessor determines the occurrence of the earthquake when data of a duration of the signal generated by the seismic-sensing element is fed to the microprocessor for a predetermined number of times within a predetermined period of time. An acceleration-sensitive device according to claim 2, wherein the seismic-sensitive element generates a signal when? subject to an oscillation due to an earthquake and the device sensitive to acceleration? connected with a microprocessor provided with data of a cycle and a response threshold value in an alternative characteristic of an oscillation due to an earthquake of an intensity? predetermined seismic, the microprocessor being programmed to compare the signal generated by the seismosensitive element with the data, in such a way that the oscillation due to the earthquake is distinguished from a disturbing oscillation so that? the microprocessor determines the occurrence of the earthquake when data of a duration of the signal generated by the seismic-sensitive element are fed to the microprocessor for a predetermined number of times within a predetermined period of time.